Hi, I'm running a 64-bit multi-threaded program on the windows server 2003 server (X64), It run into a case that some of the threads seem to be blocked in the malloc or free function forever. The stack trace is like follows:

ntdll.dll!NtWaitForSingleObject()  + 0xa bytes  
ntdll.dll!RtlpWaitOnCriticalSection()  - 0x1aa bytes    
ntdll.dll!RtlEnterCriticalSection()  + 0xb040 bytes 
ntdll.dll!RtlpDebugPageHeapAllocate()  + 0x2f6 bytes    
ntdll.dll!RtlDebugAllocateHeap()  + 0x40 bytes  
ntdll.dll!RtlAllocateHeapSlowly()  + 0x5e898 bytes  
ntdll.dll!RtlAllocateHeap()  - 0x1711a bytes    
MyProg.exe!malloc(unsigned __int64 size=0)  Line 168    C
MyProg.exe!operator new(unsigned __int64 size=1)  Line 59 + 0x5 bytes   C++


ntdll.dll!NtWaitForSingleObject()   
ntdll.dll!RtlpWaitOnCriticalSection()   
ntdll.dll!RtlEnterCriticalSection()     
ntdll.dll!RtlpDebugPageHeapFree()   
ntdll.dll!RtlDebugFreeHeap()    
ntdll.dll!RtlFreeHeapSlowly()   
ntdll.dll!RtlFreeHeap()     
MyProg.exe!free(void * pBlock=0x000000007e8e4fe0)   C

BTW, the param values passed to the new operator is not correct here maybe due to optimization.

Also, at the same time, I found in the process Explorer, the virtual size of this program is 10GB, but the private bytes and working set is very small (<2GB). We did have some threads using virtualalloc but in a way that commit the memory in the call, and these threads are not blocked.

m_pBuf = VirtualAlloc(NULL, m_size, MEM_COMMIT, PAGE_READWRITE);
......
VirtualFree(m_pBuf, 0, MEM_RELEASE);

This looks strange to me, seems a lot of virtual space is reserved but not committed, and malloc/free is blocked by lock. I'm guessing if there's any corruptions in the memory/object, so plan to turn on gflag with pageheap to troubleshoot this.

Does anyone has similar experience on this before? Could you share with me so I may get more hints?

Thanks a lot!